(57) A cartridge assembly comprising a channel including side walls and a bottom wall that define a cavity, the bottom wall defining a first knife slot that extends longitudinally through the bottom wall a staple cartridge positioned within the cavity of the channel, the staple cartridge having a body, staples, and an actuation sled, the body defining staple receiving slots and a second knife slot, the staples received within the staple receiving slots, the actuation sled movable through the body from a sled retracted position to a sled advanced position to eject the staples from the staple cartridge, the actuation sled including a ramp member that extends through the first knife slot of the channel and a locking member supported on the channel and including a finger that extends across the first knife slot, the finger being movable from a first position engaged with an outer surface of the channel to a second position spaced from the outer surface of the channel, wherein movement of the actuation sled from the sled retracted position towards the sled advanced position moves the ramp member into engagement with the finger to move the finger from the first position to the second position.